Coldworm the Burrower is a Super Unique Monster and the matriarch of the Sand Maggots of the Maggot Lair located in the Far Oasis. It has a unique model that resembles a gargantuan, queen-like bug, partially buried in the sands. It is also unofficially referred to as the Maggot Queen, implying a possible relationship with Duriel (colloqially referred to as the Maggot King).
Players will encounter Coldworm the Burrower on their quest to reassemble the Horadric Staff in Act II. A gold chest near the creature contains the Staff of Kings, the shaft portion of the aforementioned staff. How it came into the possession of the Sand Maggots is unknown.
Though Coldworm doesn't have any regular attacks, killing it can still prove to be a dangerous undertaking. The room in which Coldworm is located is filled with monsters, including Sand Maggots. Coldworm has the ability to spawn fully-grown Sand Maggots, which in turn lay and hatch eggs that spawn young. Given enough time Coldworm can spawn vast hordes of maggots and easily overwhelm even the sturdiest of heroes. Therefore it's best to clear the chamber as fast as possible.
Upon death Coldworm spills acidic blood that rains down in a large area of effect. This blood causes Poisoning and deals a fair amount of damage. If Coldworm had the ability "Cursed", this attack will also apply Amplify Damage to the character, making the situation even more hazardous. Therefore it is advised to kill Coldworm from a safe distance (for instance the tunnel leading to the chamber) with ranged spells or attacks. Necromancers may find that Corpse Explosion works great to this end.
After it's death, Coldworm's corpse can't be exploded or eaten by Druid's Vines.